a) Field of the Invention
This invention relates to a rolling screen with a screen such as an insect net or a sunshade cloth stored within a screen case. The screen is wound on a take-up shaft rotatably held within the screen case. Accordingly, the screen can be automatically arranged extending over an opening of a building or the like while winding it out of the screen case. When the screen becomes no longer needed, it can be wound back into the screen case by taking it up on the take-up shaft.
b) Description of the Related Art
Conventional rolling screens include those having a screen case arranged inside a window frame or the like. The screen case is provided with a hollow take-up shaft rotatably arranged inside the screen case. A screen, such as an insect net or a sunshade cloth, is wound on the take-up shaft so that the screen is stored within the screen case. When the screen is needed, the screen is wound out of the screen case so that it is automatically arranged extending over an opening of the window or the like. When the screen becomes no longer needed, it can be wound back into the screen case by taking it up on the take-up shaft.
Upon winding out the screen to arrange the same to extend over the opening, it is necessary to permit its smooth planar arrangement without causing a wound-out portion of the screen to wave (in other words, to undergo a so-called flaring phenomenon). When the screen is wound out and is arranged extending over the opening, pulling force is applied to the take-up shaft via the screen. The take-up shaft is therefore required to have strength sufficient to withstand such pulling force, so that the take-up shaft is protected from flexion and deformation to avoid occurrence of noise from the take-up shaft and also to permit smooth arrangement of the screen. Accordingly, it has heretofore been the practice to use, as a take-up shaft, a pipe having a large outer diameter. It has also been the practice to leave the arranged screen free at upper and lower edges thereof.
For the avoidance of the above-mentioned potential problem that the take-up shaft may be flexed and deformed by pulling force applied via the screen upon winding out the screen and during its use, and the take-up shaft may hence produce noise and/or prevent smooth winding-out and arrangement of the screen, it is essential to employ, as the take-up shaft, a pipe having strength sufficient to withstand such pulling force, i.e., having an outer diameter large enough to withstand such pulling force.
When a screen such as an insect screen is arranged extending over an opening of a building, the thus-arranged screen is exposed to wind pressure. An associated take-up shaft is therefore pulled by the screen, so that the take-up shaft may be flexed and deformed. This may lead to an inconvenience that the screen may be caused to flare at a central part thereof. As the take-up shaft for taking up and storing the screen, a pipe having an outer diameter of 20 mm or greater is in general therefore used. A screen case having large external dimensions is therefore required for the accommodation of the take-up shaft. This leads to a problem that the screen case may not be adequately arranged within a small depth of a frame of an opening of a building, for example, within a small depth of inner casing of an opening of a door or window. Especially in a construction where a rolling wire screen, which is used to prevent entry of insects, is received in a window end stile of a double sliding sash, namely, in a construction where a window end stile is provided with a channel of a square U-section which is open on a window end side of the stile, a rolled screen is stored in the channel, and a sliding glass sash is horizontally pulled or opened to cause the screen to extend over the opening, the depth of a window end stile of the double sliding sash is usually as small as 20 to 25 mm or so. As a corollary to this, the outer diameter of the take-up shaft of this rolling wire screen must be as small as 10 mm or so. The take-up shaft cannot therefore be provided with sufficient strength, possibly resulting in a substantial deformation due to flexion caused upon winding out the screen or during use of the screen. This deformation in turn results in waving of the screen, thereby making it impossible to fully achieve the object, that is, the prevention of entry of insects. In particular, as the length of a take-up shaft of a small outer diameter becomes greater, the take-up shaft tends to become more liable to arching before transmission of sufficient rotating force to the take-up shaft upon winding out the screen. It may hence become no longer possible to wind out the screen in some instances.
In the case of a horizontal rolling wire screen that a net is caused to extend in a horizontal direction over an opening of a building, a wound-out portion of the net is generally left free at its upper and lower edges. Openings therefore tend to occur between the upper and lower edges of the net and the corresponding upper and lower frames of the opening of the building, leading to a problem that the wire screen cannot fully prevent insects from entering the building. Moreover, the upper and lower edges of the net are more susceptible to stretching and slacking than a central part of the net. This results in problems that the net may be stored in a folded state upon taking it up on a take-up shaft, and the net yarns are prone to loosening at the upper and lower edges, leading to breakage of the net. As a countermeasure to this potential problem, it has therefore been proposed and practiced to sew discrete tapes such as of aluminum foil on and along the upper and lower edges of the net for their reinforcement. The sewing of tapes such as of aluminum foil or the like however results in a greater thickness at both the upper and lower edges of the net. As a result, the take-up shaft with the net wound thereon has a greater outer diameter, leading to a problem that a greater screen case must be used for the accommodation of the take-up shaft and the net wound thereon.
On the other hand, in the case of a vertical rolling wire screen where a net is caused to extend in a vertical direction, reinforcing tapes such as of aluminum foils are generally sewn on and along opposite vertical side edges of the net. The net is therefore thicker at the vertical side edges than the remaining part thereof, whereby stepped portions are formed along the vertical side edges. The reinforced vertical side edges are fitted in guide slits, specifically in lipped opposite vertical side guide rails of a square U-section, so that the reinforced vertical side edges are held slidably up and down in the corresponding lipped opposite vertical side guide rails. The opposite vertical side edges of the net can therefore be maintained within the corresponding guide rails when the net is caused to extend in a vertical direction. Friction is however developed between the reinforced opposite vertical side edges of the net and the corresponding guide rails when the net is caused to extend or is taken up. Due to this friction, greater operating force is required upon causing the net to extend or retract and especially, significant operating force is required upon causing the net to extend downwards. The above friction also causes sliding noise upon operating the net in a vertical direction. Further, when the net is exposed to external pressure and substantially large load is applied to the opposite vertical side edges of the net, the opposite vertical side edges of the net may slip out of the guide rails. If this happens, it is very difficult to repair the vertical rolling wire screen. Its repair must hence be done by a professional repairman. This is certainly very cumbersome for the user.